1. Field of the Invention
The present invention relates to navigation devices, more particularly to a navigation device of a type additionally advising a car which lane to take when guiding a way between any two locations arbitrarily designated on a map.
2. Description of the Background Art
A conventional navigation device commonly presents path information road by road to a driver. However, for safe and correct guidance of right/left turn at intersection or which road to take, path information road by road is not enough without information on lane change. This is because, even when the driver is on the right path, lane control may prevent him/her from heading for his/her destination, for example.
Accordingly, in recent years, various types of navigation devices capable of additionally guiding lanes have been developed. A typical conventional method of guiding lanes is lane graphical display. In this lane graphical display, for example, road link data directly linked to intersection nodes on a two-dimensional map is each manually provided in advance with the number of lanes and lane control information. When the car reaches a predetermined distance range of an intersection where the car is supposed to pass by, the lanes at the intersection are graphically displayed, and lane guidance information is also presented to the driver in accordance with the lane control information for the intersection.
The problem herein is, in the lane guidance information of the conventional navigation device, only path information and the number of lanes at the closest intersection are taken into consideration. Therefore, in a case where complicated-shaped intersections come along one after another, improper lane guidance information (i.e., lane change cannot be smoothly done) is often presented to the driver. This is because, for the driver to smoothly change lanes, it is not enough to concern about heading direction, the number of lanes, and lane control only at the closest intersection, but is necessary to concern about those at one or more intersections ahead. For example, when the car is on a three-lane road, and is supposed to go straight at the closest intersection and then turns left at the following intersection, it is easier for the driver to drive on a left lane to go along the path.